pacman::p_load(sf, spNetwork, tmap, tidyverse)Hands-On Exercise 03
Data Sources
(saved under ‘data’ folder)
Study Area - Punggol Planning Area
Punggol_St - line feature geospatial dataset containing road network
Punggol_CC - point feature geospatial dataset containing location of childcare centres
Chapter 7: Network Constrained Spatial Point Patterns Analysis
7.1 Setting Up
7.1.1 Loading the R packages
7.1.2 Importing spatial data
# Load network dataset
network <- st_read(dsn="data", layer="Punggol_St") # Check that geometry is Linestring and not multilinestringReading layer `Punggol_St' from data source
`C:\Users\Henry\Desktop\SMU Masters\2024-2025 T1\Geospatial Analytics & Applications\Project\GeospatialWebsite\Hands-On_Ex\Hands-On_Ex_03\data'
using driver `ESRI Shapefile'
Simple feature collection with 2642 features and 2 fields
Geometry type: LINESTRING
Dimension: XY
Bounding box: xmin: 34038.56 ymin: 40941.11 xmax: 38882.85 ymax: 44801.27
Projected CRS: SVY21 / Singapore TM# Load childcare dataset
childcare <- st_read(dsn="data", layer="Punggol_CC") %>%
st_zm(drop = TRUE, what = "ZM") # Remove Z dimensionReading layer `Punggol_CC' from data source
`C:\Users\Henry\Desktop\SMU Masters\2024-2025 T1\Geospatial Analytics & Applications\Project\GeospatialWebsite\Hands-On_Ex\Hands-On_Ex_03\data'
using driver `ESRI Shapefile'
Simple feature collection with 61 features and 1 field
Geometry type: POINT
Dimension: XYZ
Bounding box: xmin: 34423.98 ymin: 41503.6 xmax: 37619.47 ymax: 44685.77
z_range: zmin: 0 zmax: 0
Projected CRS: SVY21 / Singapore TM# See childcare features
childcareSimple feature collection with 61 features and 1 field
Geometry type: POINT
Dimension: XY
Bounding box: xmin: 34423.98 ymin: 41503.6 xmax: 37619.47 ymax: 44685.77
Projected CRS: SVY21 / Singapore TM
First 10 features:
Name geometry
1 kml_10 POINT (36173.81 42550.33)
2 kml_99 POINT (36479.56 42405.21)
3 kml_100 POINT (36618.72 41989.13)
4 kml_101 POINT (36285.37 42261.42)
5 kml_122 POINT (35414.54 42625.1)
6 kml_161 POINT (36545.16 42580.09)
7 kml_172 POINT (35289.44 44083.57)
8 kml_188 POINT (36520.56 42844.74)
9 kml_205 POINT (36924.01 41503.6)
10 kml_222 POINT (37141.76 42326.36)# See childcare crs information
st_crs(childcare)Coordinate Reference System:
User input: SVY21 / Singapore TM
wkt:
PROJCRS["SVY21 / Singapore TM",
BASEGEOGCRS["SVY21",
DATUM["SVY21",
ELLIPSOID["WGS 84",6378137,298.257223563,
LENGTHUNIT["metre",1]]],
PRIMEM["Greenwich",0,
ANGLEUNIT["degree",0.0174532925199433]],
ID["EPSG",4757]],
CONVERSION["Singapore Transverse Mercator",
METHOD["Transverse Mercator",
ID["EPSG",9807]],
PARAMETER["Latitude of natural origin",1.36666666666667,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8801]],
PARAMETER["Longitude of natural origin",103.833333333333,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8802]],
PARAMETER["Scale factor at natural origin",1,
SCALEUNIT["unity",1],
ID["EPSG",8805]],
PARAMETER["False easting",28001.642,
LENGTHUNIT["metre",1],
ID["EPSG",8806]],
PARAMETER["False northing",38744.572,
LENGTHUNIT["metre",1],
ID["EPSG",8807]]],
CS[Cartesian,2],
AXIS["northing (N)",north,
ORDER[1],
LENGTHUNIT["metre",1]],
AXIS["easting (E)",east,
ORDER[2],
LENGTHUNIT["metre",1]],
USAGE[
SCOPE["Cadastre, engineering survey, topographic mapping."],
AREA["Singapore - onshore and offshore."],
BBOX[1.13,103.59,1.47,104.07]],
ID["EPSG",3414]]# See network features
networkSimple feature collection with 2642 features and 2 fields
Geometry type: LINESTRING
Dimension: XY
Bounding box: xmin: 34038.56 ymin: 40941.11 xmax: 38882.85 ymax: 44801.27
Projected CRS: SVY21 / Singapore TM
First 10 features:
LINK_ID ST_NAME geometry
1 116130894 PUNGGOL RD LINESTRING (36546.89 44574....
2 116130897 PONGGOL TWENTY-FOURTH AVE LINESTRING (36546.89 44574....
3 116130901 PONGGOL SEVENTEENTH AVE LINESTRING (36012.73 44154....
4 116130902 PONGGOL SEVENTEENTH AVE LINESTRING (36062.81 44197....
5 116130907 PUNGGOL CENTRAL LINESTRING (36131.85 42755....
6 116130908 PUNGGOL RD LINESTRING (36112.93 42752....
7 116130909 PUNGGOL CENTRAL LINESTRING (36127.4 42744.5...
8 116130910 PUNGGOL FLD LINESTRING (35994.98 42428....
9 116130911 PUNGGOL FLD LINESTRING (35984.97 42407....
10 116130912 EDGEFIELD PLNS LINESTRING (36200.87 42219....# See network crs information
st_crs(network)Coordinate Reference System:
User input: SVY21 / Singapore TM
wkt:
PROJCRS["SVY21 / Singapore TM",
BASEGEOGCRS["SVY21",
DATUM["SVY21",
ELLIPSOID["WGS 84",6378137,298.257223563,
LENGTHUNIT["metre",1]]],
PRIMEM["Greenwich",0,
ANGLEUNIT["degree",0.0174532925199433]],
ID["EPSG",4757]],
CONVERSION["Singapore Transverse Mercator",
METHOD["Transverse Mercator",
ID["EPSG",9807]],
PARAMETER["Latitude of natural origin",1.36666666666667,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8801]],
PARAMETER["Longitude of natural origin",103.833333333333,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8802]],
PARAMETER["Scale factor at natural origin",1,
SCALEUNIT["unity",1],
ID["EPSG",8805]],
PARAMETER["False easting",28001.642,
LENGTHUNIT["metre",1],
ID["EPSG",8806]],
PARAMETER["False northing",38744.572,
LENGTHUNIT["metre",1],
ID["EPSG",8807]]],
CS[Cartesian,2],
AXIS["northing (N)",north,
ORDER[1],
LENGTHUNIT["metre",1]],
AXIS["easting (E)",east,
ORDER[2],
LENGTHUNIT["metre",1]],
USAGE[
SCOPE["Cadastre, engineering survey, topographic mapping."],
AREA["Singapore - onshore and offshore."],
BBOX[1.13,103.59,1.47,104.07]],
ID["EPSG",3414]]7.2 Visualize Geospatial Data
# Visualize both geospatial data
plot(st_geometry(network)) # Use st_geometry to plot only the network without corresponding attributes
plot(childcare,add=T,col='red',pch = 19)
# Interactive Visualization with tmap
tmap_mode('view')tmap mode set to interactive viewingtm_shape(childcare) +
tm_dots() +
tm_shape(network) +
tm_lines()# Set tmap_mode back to plot
tmap_mode('plot')tmap mode set to plotting7.3 Network KDE (NKDE) ANalysis
7.3.1 Prepare Lixel Objects
# Cut spatiallines objects into lixels with specified minimal distance using lixelize_lines from spNetwork
lixels <- lixelize_lines(network, 700, mindist = 375)
# Use nearest neighbour to gauge the appropriate distance - bottom ~25%-10%7.3.2 Generate line centre points
# create line centre points with lines_center from spNetwork
samples <- lines_center(lixels)
tmap_mode('view')tmap mode set to interactive viewingtm_shape(lixels) +
tm_lines() +
tm_shape(samples) +
tm_dots(size =0.01)tmap_mode("plot")tmap mode set to plotting7.3.3 Perform NKDE
# # Remove Z-dimension from childcare (No longer required)
# childcare_rmz <- st_zm(childcare)
# Perform NKDE
densities <- nkde(network,
events = childcare,
w = rep(1, nrow(childcare)),
samples = samples,
kernel_name = "quartic", # Try to avoid gaussian if intensity is negative
bw = 300,
div= "bw",
method = "simple",
digits = 1,
tol = 1,
grid_shape = c(1,1),
max_depth = 8,
agg = 5,
sparse = TRUE,
verbose = FALSE)
# Densities - represents intensity# Insert computed density values as density field
samples$density <- densities
lixels$density <- densities
# Recaling to enhance mapping
samples$density <- samples$density*1000
lixels$density <- lixels$density*1000
# Visualize interactive plot
tmap_mode('view')tmap mode set to interactive viewingtm_shape(lixels)+
tm_lines(col="density")+
tm_shape(childcare)+
tm_dots()tmap_mode('plot')tmap mode set to plotting7.4 Network Constrainted G- and K- Function Analysis
Ho: The observed spatial point events (i.e distribution of childcare centres) are uniformly distributed over a street network in Punggol Planning Area.
# Perform complete spatial randomness test using kfunction from spNetwork
kfun_childcare <- kfunctions(network,
childcare,
start = 0,
end = 1000,
step = 50,
width = 50,
nsim = 50, # 51 simulations
resolution = 50,
verbose = FALSE,
conf_int = 0.05)# Visualize k-function output
kfun_childcare$plotk
Conclusion
- There is non complete spatial randomness
- In certain distances (~250-500), childcares are regularly spaced out
- At higher distances (>600), childcares are randomly spaced out